The invention is directed to a process for the resolution of the racemate (1RS,2SR)-2-amino-1-phenyl-propan-1-ol, especially for the purpose of recovery of (1R,2S)-2-amino-1-phenyl-propan-1-ol. This substance is an important starting material for the synthesis of medicines.
It is known to separate (1R,2S)-2-amino-1-phenyl-propan-1-ol, also called 1-norephedrine, from the racemate (1RS,2SR)-2-amino-1-phenyl-propan-1-ol by means of optically active tartaric acid (Nagai, Liebigs Ann. Chem. Vol. 470, pages 157-182 (1929)). This process is unsatisfactory because the diastereomer salts involved are only slightly different in their solubility.
Besides, it is known to resolve the racemate (1RS,2SR)-2-amino-1-phenyl-propan-1-ol by means of the optical isomers of 3-formyl-2,2,5,5-tetramethylthiazolidin-4-carboxylic acid (German patent 2138121 and related Asinger U.S. Pat. No. 3,959,302. The entire disclosure of Asinger is hereby incorporated by reference and relied upon). The diastereomeric salts involved have moderately good solubility differences, but a disadvantage of this process is that the thiazolidine-carboxylic acid has only slight stability.